Impulse, Momentum Change, and Collision Forces

All flashcards

How is impulse calculated for a time-varying force?

$\vec J=\int_{t_i}^{t_f}\vec F(t)\,dt$.

What is the SI unit of impulse?

The newton-second (N·s), equivalent to kg·m/s.

What does the impulse–momentum theorem state?

$\vec J=\Delta\vec p$: impulse equals the change in momentum.

How does a longer collision time affect average force for the same momentum change?

It reduces the average force magnitude because $F_{avg}=\Delta p/\Delta t$.

Why is the momentum form of Newton's second law useful for changing-mass systems?

$\vec F_{net}=d\vec p/dt$ applies without treating mass as constant.

Quiz questions

1. What is the impulse–momentum theorem?Answer: Impulse equals the object's change in momentum.
2. For the same momentum change, what happens to average force if collision duration increases?Answer: The average force magnitude decreases.
3. In instantaneous form, what does Newton's second law equate to net external force?Answer: The rate of change of momentum.
4. For an object of constant mass, which expression follows from $\vec F_{net}=d\vec p/dt$?Answer: $\vec F_{net}=m\vec a$.
5. Why does estimating peak collision force require choosing a force-versus-time model?Answer: The impulse fixes the area, but different force profiles can have different peaks.